1. Article purpose[edit | edit source]
The purpose of this article is to:
- briefly introduce the DCMI peripheral and its main features,
- indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
- list the software frameworks and drivers managing the peripheral,
- explain how to configure the peripheral.
2. Peripheral overview[edit | edit source]
The DCMI (digital camera memory interface) peripheral is used to receive some video data from an external parallel camera sensor device or any other digital video equipment supporting parallel interface.
The DCMI hardware block can receive raw data frames in RGB565 and YUV422 formats as well as JPEG compressed data.
Refer to the STM32 MPU reference manuals for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.
Refer to STM32 DCMI presentation [1] for an overview of DCMI hardware block and its capabilities.
3. Peripheral usage[edit | edit source]
This chapter is applicable in the scope of the OpenSTLinux BSP running on the Arm® Cortex®-A processor(s), and the STM32CubeMPU Package running on the Arm® Cortex®-M processor.
3.1. Boot time assignment[edit | edit source]
3.1.1. On STM32MP15x lines 
[edit | edit source]
The DCMI peripheral is not used at boot time.
3.1.2. On STM32MP2 series[edit | edit source]
Click on 
to expand or collapse the legend...
- ☐ means that the peripheral can be assigned to the given boot time context.
- ☑ means that the peripheral is assigned by default to the given boot time context and that the peripheral is mandatory for the Yocto-based OpenSTLinux Embedded Software.
- ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32 MPU reference manuals.
| Domain | Peripheral | Boot time allocation | Comment
| |||
|---|---|---|---|---|---|---|
| Instance | Cortex-A35 secure (ROM code) |
Cortex-A35 secure (TF-A BL2) |
Cortex-A35 nonsecure (U-Boot) | |||
| Visual | DCMI | DCMI | ⬚ | |||
3.2. Runtime assignment[edit | edit source]
3.2.1. On STM32MP15x lines [edit | edit source]
Click on to expand or collapse the legend...
Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:
- ☐ means that the peripheral can be assigned to the given runtime context.
- ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.
| Domain | Peripheral | Runtime allocation | Comment
| |||
|---|---|---|---|---|---|---|
| Instance | Cortex-A7 secure (OP-TEE) |
Cortex-A7 non-secure (Linux) |
Cortex-M4 (STM32Cube) | |||
| Visual | DCMI | DCMI | ☑ | ☐ | Assignment (single choice) | |
3.2.2. On STM32MP21x lines [edit | edit source]
Click on to expand or collapse the legend...
Check boxes illustrate the possible peripheral allocations supported by Yocto-based OpenSTLinux Embedded Software:
- ☐ means that the peripheral can be assigned to the given runtime context.
- ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the Yocto-based OpenSTLinux Embedded Software.
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP21 reference manuals.
| Domain | Peripheral | Runtime allocation | Comment
| ||||
|---|---|---|---|---|---|---|---|
| Instance | Cortex-A35 secure (OP-TEE / TF-A BL31) |
Cortex-A35 nonsecure (Linux) |
Cortex-M33 secure (TF-M) |
Cortex-M33 nonsecure (STM32Cube) | |||
| Visual | DCMI | DCMI | ⬚OP-TEE | ☑ | ⬚ | ☐ | |
3.2.3. On STM32MP23x lines [edit | edit source]
Click on to expand or collapse the legend...
Check boxes illustrate the possible peripheral allocations supported by Yocto-based OpenSTLinux Embedded Software:
- ☐ means that the peripheral can be assigned to the given runtime context.
- ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the Yocto-based OpenSTLinux Embedded Software.
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP23 reference manuals.
| Domain | Peripheral | Runtime allocation | Comment
| ||||
|---|---|---|---|---|---|---|---|
| Instance | Cortex-A35 secure (OP-TEE / TF-A BL31) |
Cortex-A35 nonsecure (Linux) |
Cortex-M33 secure (TF-M) |
Cortex-M33 nonsecure (STM32Cube) | |||
| Visual | DCMI | DCMI | ⬚OP-TEE | ☑ | ⬚ | ☐ | |
3.2.4. On STM32MP25x lines [edit | edit source]
Click on to expand or collapse the legend...
Check boxes illustrate the possible peripheral allocations supported by Yocto-based OpenSTLinux Embedded Software:
- ☐ means that the peripheral can be assigned to the given runtime context.
- ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the Yocto-based OpenSTLinux Embedded Software.
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP25 reference manuals.
| Domain | Peripheral | Runtime allocation | Comment
| |||||
|---|---|---|---|---|---|---|---|---|
| Instance | Cortex-A35 secure (OP-TEE / TF-A BL31) |
Cortex-A35 nonsecure (Linux) |
Cortex-M33 secure (TF-M) |
Cortex-M33 nonsecure (STM32Cube) |
Cortex-M0+ (STM32Cube) | |||
| Visual | DCMI | DCMI | ⬚OP-TEE | ☑ | ⬚ | ☐ | ||
4. Software frameworks and drivers[edit | edit source]
Below are listed the software frameworks and drivers managing the DCMI peripheral for the embedded software components listed in the above tables.
- Linux®: V4L2 framework
- STM32Cube:
- for STM32MP15x lines : DCMI HAL driver and header file of DCMI HAL module
- for STM32MP2 series: DCMI HAL driver and header file of DCMI HAL module
- for STM32MP15x lines
5. How to assign and configure the peripheral[edit | edit source]
The peripheral assignment can be done via the STM32CubeMX graphical tool (and manually completed if needed).
This tool also helps to configure the peripheral:
- partial device trees (pin control and clock tree) generation for the OpenSTLinux software components,
- HAL initialization code generation for the STM32CubeMPU Package.
The configuration is applied by the firmware running in the context in which the peripheral is assigned.
See also additional information in the DCMI device tree configuration article for Linux®.
6. How to go further[edit | edit source]
Refer to STM32 DCMI Application Note (AN5020)[2] for a detailed description of the DCMI peripheral and applicable use-cases.
This application note is related to STM32 microcontrollers but it is also applicable to STM32 MPUs. This document can help to better understand stm32-dcmi V4L2 kernel driver and debug camera sensor and DCMI interactions.
7. References[edit | edit source]
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere. 
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.